Icon Cancer Centre, Windsor Gardens, SA, Australia.
Icon Cancer Centre, Moreland, VIC, Australia.
J Radiol Prot. 2021 Nov 18;41(4). doi: 10.1088/1361-6498/ac2e0b.
Linear accelerator bunker shielding protocols such as NCRP 151 have previously been tested against a large sample of measured data from real bunkers and machines but differences in per-energy concrete penetration (TVLs) for 10 MV has not yet been resolved. These differences are likely due to historical beam data and can potentially result in over-exposure of radiation workers and the public. This study examines a cohort of clinical linac bunker survey measurements and compares them to popular shielding protocols. Differences were investigated using contemporary beam data for both Monte Carlo simulation and in analytical equations. For primary barriers, NCRP 151 underestimates the dose rate through concrete by on average a factor of 2 with secondary barriers and maze entrance doses having much better agreement. Use of contemporary beam data in Monte Carlo simulation and an analytical equation yielded TVL values much closer to the measured values compared to NCRP 151. The TVL data in NCRP 151 is outdated and needs to be updated based upon the energy spectra of modern linear accelerators. Until then, physicists should use the TVL values shown in this study instead.
线性加速器掩体屏蔽协议，如 NCRP 151，之前已经针对来自真实掩体和机器的大量实测数据进行了测试，但 10MV 的每能量混凝土穿透量 (TVLs) 差异尚未得到解决。这些差异可能是由于历史光束数据引起的，并可能导致辐射工作人员和公众受到过度辐射。本研究检查了一组临床直线加速器掩体调查测量结果，并将其与流行的屏蔽协议进行了比较。使用当代光束数据进行了差异调查，包括蒙特卡罗模拟和分析方程。对于主要屏蔽，NCRP 151 平均低估了混凝土中的剂量率，而对于次要屏蔽和迷宫入口剂量，其一致性要好得多。与 NCRP 151 相比，在蒙特卡罗模拟和分析方程中使用当代光束数据可产生更接近实测值的 TVL 值。NCRP 151 中的 TVL 数据已经过时，需要根据现代直线加速器的能谱进行更新。在那之前，物理学家应该使用本研究中显示的 TVL 值。
